A number of methods have been devised to apply colour or tints to paint. Typically, multiple pigments are separately added to a paint base at either a central location by the paint manufacturer or at the point of sale by a paint retailer to achieve a predetermined paint colour. Both of these approaches have significant limitations.
In the central production model the range of colours is typically limited due to economies of scale, meaning there is little scope for bespoke or low-volume colour production, and logistics of stock holding and transport of the factory-coloured paint limits the practical delivery of a full colour range.
Retail-tinted paint systems rely on human control or a mix of computer control and human programming to accurately tint paints from a low number of separate, single liquid pigments. Each pigment has to be carefully dosed volumetrically by a complex machine in the retail environment by semi-skilled operators according to a formulation provided by the pigment manufacturer, posing a risk of mis-tinting. Further, liquid pigments typically utilise Volatile Organic Compounds (VOCs), have a propensity to dry and clog the dosing machine, and require mechanical mixing in-store.
A further disadvantage of both central production and retail colouring is limited access to design-led colour palettes and the need to engage with the physical paint retail channel.
Dry pigment formulation systems have been developed for paint that can be easily dispersed using minimal mechanical intervention. These pigments are called Easily Dispersed or ED pigments and have been successfully used in the central production of paints and the tinting of concrete at the point of use. The opportunity to use ED pigments at the point of sale of paint, has been identified and a number of systems for formulating mixtures of ED pigments at the point of sale have been explored. For example, U.S. Pat. Nos. 7,311,223 and 7,134,573 describe systems for point of sale dispensing of dry pigment formulations. As ED pigments are particularly concentrated they require very accurate formulation (weighing) which has resulted in proposed retail machines that require very high levels of accuracy and calibration. However, in practice these systems have been impractical and further compromised the quality of the tinted paint, suffering from the same accuracy and user skill problems as do point of sale systems for dispensing liquid formulations. Further, the range of ED pigments is limited, further limiting the potential of retail systems.
As an alternative to incumbent processes, packaging of pigments, including ED pigments, for small volume paint requirements has been proposed. U.S. Patent Publication US 2007/0221531 discloses dissolvable packets containing a predefined quantity of dry powder dispersible pigments that, when added to a predetermined volume of a compatible liquid coating, dissolves in the container to tint the coating. U.S. Patent Publication US 2007/0266901 discloses encapsulated formulations provided as a system and kit, wherein the encapsulating layer is in the form of a sealed pouch that contains the tinting material. Multiple pouches, each having different tinting materials, may be combined to provide a colour range of up to about 150 different colours or shades. The pouches are packaged in a moisture resistant package or container. U.S. Patent Publication US 2003/0060553 discloses pressing single pigment preparations to form dispersible single pigment preparations in the form of pellets or tablets. Pigment portions are marketed in different portion amounts, providing more or less intensive base colours, which may then be mixed with other pigments.
A limitation on the use of commercially-available ED pigments is the limited colour range available in this format. Further, where sold as a final pigment mixture, the different ED dry pigment formulations are mixed in the carrier (pouch/pack/tablet), which does not produce a colour indicative of the final paint colour, making the package less attractive/suitable for display and unsuitable for visual matching or checking with a required colour, prior to mixing into the paint.
NZ207217 proposes a solid paint concentrate including a pigment or mixture of pigments. A final paint colour may be reached by selecting a number of pigment concentrates corresponding to the desired colour. While overcoming some of the limitations of existing systems through the use of a solid, pre-manufactured paint concentrate the prior art tablet systems do not overcome the limitations of the retail environment with respect to mis-tinting risk. Further, the tablet formulations disclosed in the prior art do not disperse effectively without the use of a retail mechanical mixer, thus limiting the sale of colour outside the paint retail channel.
In addition to the limitations of the formulations, methods and systems discussed above, the cost of pigments can be a substantial portion of the total cost of raw materials used in the manufacture of coloured media, including surface coatings such as paints. Individual pigments are processed and formulated in order to optimise their performance when added to a specific base medium. The sought after performance characteristics of these pigment preparations include stability during storage, rapid and uniform dispersibility on mixing with the base medium, and long-term maintenance of the appearance of the coloured medium, e.g. resistance to fading. The art is replete with methods of processing and formulating pigments where the objective is to optimise the performance of a single class of pigment. Examples include the methods disclosed in the publications of Aoba et al (2001), McKay (1973), Thomspon et al (2009) and Wilkinson (1966).
The publication of Aoba et al (2001) discloses a composite pigment of a blueish-green colour. The composite pigment comprises copper phthalocvanine and aluminium phthalocyanine. The composite is prepared by kneading a mixture of the independently comminuted pigments and resin so as to disperse the pigments in the resin. The publication of McKay (1973) discloses flocculation resistant phthalocyanine pigments. The pigments are prepared by milling a combination of a phthalocyanine pigment, a chloromethylated phthalocyanine compound and organic amines. Cyclohexylamines and n-butylamine are discloses as examples of organic amines used in the preparation of the pigments. The publication of Thomspon et al (2009) discloses quinacridone products used for colouring a variety of base media including paints. The products are crystal forms of solid solutions of 2,9-dimethyoxyquinacridone and 2,9-dichloroquinacridone. The publication of Wilkinson (1966) discloses solid solutions or mixed crystals in which at least one other component is a thiachromonoacridone. The pigment is provided as a solid solution as opposed to a formulation.
Further processing of such pigment preparations may still be required to ensure a base medium in which the primary particles of the pigment are uniformly dispersed is obtained. Additives may be required during this further processing to prevent excessive foaming and loss of capacity. Where pigment formulations are used to prepare coloured media at the point-of-sale (PoS) the capacity and time for further processing is limited. As noted above, liquid pigment formulations have been used in PoS operations. The primary particles of the pigment may be regarded as being in a partially “pre-dispersed” state in these formulations. A need therefore exists for a formulation that permits a plurality of different pigment preparations to be prepared in a dry form that is easily and rapidly dispersible in a base medium. Examples of dry forms of pigment formulation asserted to be easily and rapidly dispersible in a base medium are disclosed in the publications of Rance et al (2007), Reischer and Gomez (2007), Reisacher et al (2008), Ortalano et al (2008), Tauber et al (2010), Plueg and Lopez (2010), Wenning and Loest (2010), Roy et al (2010) and Kruithof et al (2010).
The publication of Ranee et al (2007) discloses pigment granules including mixtures of various organic or various inorganic pigments or mixtures of organic and inorganic pigments. In addition to these “tinting materials” the granules are disclosed as optionally containing at least one non-ionic surface-active additive based on polyethers such as unmixed polyalkylene oxides, like polyethylene oxides and polypropylene oxides, or alkylene oxide block copolymers or copolymers comprising polypropylene oxide and polyethylene oxide blocks. The publication states that the unmixed polyalkylene oxides and copolymers comprising polypropylene oxide and polyethylene oxide blocks are obtainable by polyaddition of the alkylene oxides to saturated or unsaturated aliphatic and aromatic alcohols and aliphatic amines. Suitable alkylene oxide block copolymers that are known and commercially available are identified in the publication by the trade names TETRONIC™ and PLURONIC™. These trade name products include alkoxyiated adducts such as ethylenediamine tetrakis (ethoxylate-block-propoxylate) tetrol (BASF). The publication further states that alkylene oxide block copolymers may be selected with different hydrophilic-lipophilic balance values according to the medium in which the pigment granules are to be used, but does not appear to disclose any examples of formulations containing these formulants.
The publication of Reischer and Gomez (2007) discloses pigment preparations asserted to be comparable to liquid pigment formulations with regard to colour properties and dispersibility, but not requiring the addition of dried-crust inhibitors, freeze resistance enhancers and anti-skinners. The publication states that simply drying a liquid formulation does not provide solid pigment preparations having comparable application properties. The publication discloses pigment formulations including as an essential ingredient from 10 to 40% by weight of at least one non-ionic surface-active additive based on polyethers, The pigment granules disclosed are prepared by wet comminuting the pigment as an aqueous suspension in the presence of at least some of the non-ionic surface active additive. The suspension is then spray dried following addition of the balance of the additive. The additive melts at the drying temperatures used leading to the formation of substantially spherical granules. The additive used in the examples is a block copolymer based on either ethylenediamine/propylene oxide/ethylene oxide or propylene oxide/ethylene oxide as the additive. It is stated that the block copolymers are selected with different hydrophilic-lipophilic balance values depending on the application medium in which the pigment granules are to be used. The median particle size of the single pigment granules is disclosed to be in the range 270 to 330 μm. Examples of pigment granules including only a single pigment are disclosed.
The publication of Reisacher et al (2008) discloses solid pigment preparations comprising as essential constituents at least one pigment, at least one water-soluble surface active additive and an antioxidant. A filler (without self-colour) is an optional component of the “colour conferring component” comprising the pigment. Examples of formulations comprising a block copolymer based on propylene oxide/ethylene oxide as the water-soluble surface active additive and tetrakis [methylene (3,5-di(tert-butyl) -4-hydroxyhydro-cinnamate)]methane (IRGANOX™ 1010), octadecyl 3,5-di-tert-butyl)-4-hydroxyhydroycinnamate (IRGANOX™ 1076) and tris[2,4-di(tert-butylphenyl)phosphite (IRGAFOS™ 168) as antioxidants are disclosed. The examples comprise a single pigment and do not include a filler. The antioxidant is included to stabilise the pigment preparations so they can be dried at temperatures of greater than 70° C. without, risk of auto-ignition.
The publication of Ortalano et al (2008) discloses a stir-in pigment composition. The composition comprises one or more acetylenic-based surface-active agents. The publication of Tauber et al (2010) discloses pigment preparations comprising poly(alkyl ether). The publication of Plueg and Lopez (2010) discloses universal stir-in pigment preparations containing an additive based on polyalkylene glycols. The additive is an amino derivative of a polyalkylene glycol. The publication of Wenning and Loest (2010) discloses compositions for producing universal pigment preparations containing a combination of a block-copolymeric styrene oxide-containing polyalkylene oxide and a ketone-aldehyde resin. Surprisingly, the combination was found to be soluble in water. The publications of Roy et al (2010) and Kruithof et al (2010) disclose solid preparations comprising a pigment and a dispersant resin. The dispersant resins are polymers having pendant hydrophilic polyalkylene oxide side groups.
Despite these many alternatives the need for a formulation that permits a plurality of different pigment preparations to be prepared in a dry form that is consistently, easily and rapidly dispersible in a base medium remains.
It is an object of the invention to provide improved methods, paint systems and/or dispensing systems that address one or more of the problems identified above. In particular, it would be desirable to separate the final paint colour from technical inaccuracies and user skill at the point of sale. It would also be desirable in some (but not all) applications to allow the sale of colour to be separate from the sale of base paint, enabling consumer access to bespoke colours and the procurement of colour through non-traditional sales channels separate from the base paint. It is an object of the present invention to provide a combination of formulants that permit a plurality of different pigment preparations to be prepared in a dry, flowable, particulate form suitable for use in the improved methods and systems. It is an object of the present invention to provide an improved method of colouring base media such as paint at the point-of-sale. These objects are to be read in the alternative with the object at least to provide the public with a useful choice.
Reference to any publication or other prior art does not constitute an admission that such prior art forms part of the common general knowledge.